Apparatus for transferring load between a towing tractor and a towed above ground implement.
At present problems are often encountered when tractors are used for towing above ground implements such as seed drills, scoops, large trailers and cultivating discs. In general, these problems arise due to the tractor and/or towed implement encountering:
Obstructions e.g. rocks
Muddy or wet ground
Hills or hollows
The above situations cause problems as they can adversely affect the traction of the tractor""s driving wheels and render the towing of such implements a dead weight dragging operation.
The above difficulties are currently overcome by using tractors which have:
Ballast added; or
Increased horse power/weight; and/or
Four wheel drive; and/or
Dual wheels.
However, as will be appreciated the above remedies suffer from either increasing the cost of the tractor required to perform the job, or adding time and effort to the job due to having to add ballast to the tractor.
In relation to underground working implements such as ploughs and rotary hoes, the above mentioned difficulties for towed implements have been overcome by the implementation of a hydraulic draft control system associated with the three-point linkage of a tractor. The draft control system operates by either raising or lowering the implement depending on whether its effective load has bee increased or decreased. By this means, the draft control system is able to transfer load (weight) between the implement and tractor to maintain the desired degree of wheel slippage.
It would therefore be an advantage if there could be provided some means by which the draft control system already present on many tractors could be utilised in the towing of above ground implements also.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
According to one aspect of the present invention there is provided apparatus for transferring load between:
a towing tractor which includes:
a) a three-point linkage which includes three linkage arms; and associated hydraulic draft control system; and
b) a tow-bar; and
a towed above ground implement which includes a draw-bar which attaches to the tow-bar of the tractor,
characterised in that the apparatus includes a shock absorber which is:
(i) directly or indirectly connected at one end thereof to at least the two lower arms of the tractor""s three-point linkage, and
(ii) at the other end thereof is connected either directly or indirectly to the draw-bar of the towed implement in a manner that allows the draft control system of the tractor to be activated so as to transfer load between the tractor and the implement, as is required to maintain the desired wheel slippage of the tractor""s traction axle whilst towing the implement.
According to one aspect of the present invention there is provided apparatus for transfering load between:
a towing tractor which includes:
a) a three-point linkage which includes three linkage arms; and associated hydraulic draft control system; and
b) a tow-bar; and
a towed above ground implement which includes a draw-bar which attaches to the tow-bar of the tractor;
characterised in that the apparatus includes a shock absorber which is:
i) directly or indirectly connected to the three arms of the tractor""s three-point linkage, and
ii) at the other end thereof is connected either directly or indirectly to the draw bar of the towed implement in a manner that allows:
the shock absorber to experience a force which is forward of the towed implement; and
the draft control system of the tractor to be activated so as to transfer load between the tractor and the implement, as is required to maintain the desired wheel slippage of the tractor""s traction axle whilst towing the implement;
such that load from the towed implement can be transferred to all the wheels of the tractor.
According to another aspect of the present invention there is provided a method of transferring load between:
a towing tractor which includes:
a) a three-point linkage which includes three linkage arms and associated hydraulic control system; and
b) a tow-bar; and
a towed above ground implement which includes a draw-bar which attaches to the tow-bar of the tractor;
the method characterised by the steps of:
(i) directly or indirectly connecting a shock absorber to at least the two lower arms of the tractors three-point linkage, and
(ii) connecting the opposite end of the shock absorber to the draw-bar of the towed implement in a manner that allows the draft control system of the tractor to be activated, and
(iii) tensioning the shock absorber by raising or lowering the tractor""s three-point linkage arms so as to enable the transfer of load between the tractor and the implement, such as required to maintain the desired wheel slippage of the tractor""s traction axle while towing the implement.
According to a further aspect of the present invention there is provided a method of transferring load between:
a towing tractor which includes:
a) a three-point linkage which includes three linkage arms and associated hydraulic control system; and
b) a tow-bar; and
a towed above ground implement which includes a draw-bar which attaches to the tow-bar of the tractor;
the method characterised by the steps of:
(i) directly or indirectly connecting a shock absorber to the three arms of the tractors three-point linkage, and
(ii) connecting the opposite end of the shock absorber to the draw-bar of the towed implement in a manner that allows:
the shock absorber to experience a force which is forward of the towed implement; and
the draft control system of the tractor to be activated, such that load from the towed implement can be transferred to all wheels of the tractor, and
(iii) tensioning the shock absorber by raising or lowering the tractor""s three-point linkage arms so as to enable the transfer of load between the tractor and the implement, such as required to maintain the desired wheel slippage of the tractor""s traction axle while towing the implement.
It is envisaged that the towing tractor may be any tractor with the characteristics referred to above.
The towed above ground implement may include:
Trailers
Scoops
Seed drills
Cultivating discs
However, this list should not be seen as limiting as the present invention may also be applied to other implements which are attached to the tow-bar of the tractor.
The shock absorber may come in a variety of different forms.
In general, the shock absorber should be capable of supporting a 3-4 ton load.
In some embodiments the shock absorber may be a gas strut or hydraulic ram.
In other embodiments the shock absorber may be a helical spring or other resilient-type member/device.
In preferred embodiments the shock absorber may be a leaf spring.
For ease of reference only, the shock absorber will now be referred to as being a leaf spring. However, it should be appreciated that the principles stated for this embodiment may also have general application to other embodiments where the shock absorber is not a leaf spring.
The leaf spring may be connected to at least the two lower arms of the tractor""s three-point linkage in a variety of different ways.
In general, the leaf spring may be attached to these arms via a mounting-frame which connects to the terminal ends of the tractors linkage arms.
In preferred embodiments, the mounting-frame may connect to all three arms of the three-point linkage.
In some preferred embodiments, the leaf spring may be pivotally attached to the mounting-frame so as to allow for any lateral movement of the towed implement. In general, the applicant has found this is best achieved by having the leaf spring pivot along the same axis, as that which the draw-bar of the implement pivots with respect to the tow-bar of the tractor.
In other preferred embodiments the leaf spring is fixedly attached to the mounting-frame but is connected to the draw-bar of the towed implement in a manner which caters for any lateral movement of the towed implement.
The leaf spring may be connected to the draw-bar of the towed implement in a variety of different ways. In general, the leaf spring should be connected to the draw-bar so that a pre-set tension can always be maintained on the leaf spring through operation of the draft control system.
In preferred embodiments, the leaf spring may be directly or indirectly connected to the draw-bar of the tractor via at least one chain.
In some other embodiments the leaf spring may be directly or indirectly connected to the draw-bar of the tractor via at least one length of wire rope.
Other methods/devices for attaching the leaf spring to the draw-bar are of course envisaged.
For ease of reference only, the leaf spring may now be thought of as being indirectly or directly connected to the draw-bar by at least one chain.
In preferred embodiments (where the leaf spring is pivotally attached to the mounting-frame), a chain may directly attach the leaf spring to the draw-bar. In such embodiments the length of the chain should be roughly equivalent to half of the distance, by which the draft control system can raise or lower the three-point linkage arms. This length of chain has been found by the applicant to allow the leaf spring to retain a tensioned connection to the draw-bar of the towed implement, whilst the implement is being lifted, or lowered, by the draft control system.
In preferred embodiments (where the leaf spring is fixedly attached to the mounting-frame), a first chain may connect the leaf spring to a bell crank (i.e. a pivoting device) which is attached to the tow-bar of the tractor. The bell crank being positioned forward of the point where the first chain is attached to the leaf spring. Attached to the other side of the bell crank may be a second chain which is connected to a substantially vertically inclined chain attachment arm, extending from the draw-bar of the towed implement. In such embodiments it is important that the second chain be connected to the bell crank in a manner that allows it to vertically and horizontally pivot. In preferred embodiments, this may be achieved via a shackle arrangement situated above the point where the draw-bar of the implement pivots with respect to the tow-bar of the tractor.
The applicant has found one advantage of preferred embodiments such as this, is that the two chain arrangement can help ensure the pre-set tension is always maintained on the leaf springxe2x80x94even when the particular type of draft control system employed by a tractor is not especially sensitive.
Another advantage of such preferred embodiments is that should the hitchpin (connecting the tractor tow-bar to the implement draw-bar), break the second chain can function as a safety chain. This is because the second chain (where connected to the tractor) has a center of gravity positioned similarly to that of the draw-bar. Furthermore, the applicant has found preferred embodiments such as this allow the leaf spring to experience a forward force so as to enable the load from the towed implement to be transferred to all the wheels of the tractor (i.e. including the front xe2x80x9csteeringxe2x80x9d wheels).
In order to allow the draft control system to be activated via an increase or decrease in the effective towed load, the leaf spring should be attached to the draw-bar and tensioned (by rang or lowering the three-point linkage arms) so the leaf spring is capable of experiencing:
(i) a vertical load; and
(ii) a rearward load with respect to the direction in which the implement is being towed.
The above requisites for attaching the leaf spring to the draw-bar ensure it is able to absorb any vertical forces associated with a change in the effective load of the implement, as well as relay a rearward load on the lower arms of the three-point linkage. It being the rearward load on the three-point linkage which activates the draft control sensing valves which in turn activate the hydraulic draft control system.
In embodiments where the leaf spring is pivotally mounted to the mounting-frame, the above tensioning objectives may be achieved by attaching the chain to both the leaf spring and the draw-barxe2x80x94such that it has an angle substantially between 30-75 degrees with respect to the draw-bar. Preferably in such embodiments this angle may be substantially 45 degrees with respect to the implements draw-bar.
In embodiments where the leaf spring is fixedly attached to the mounting frame, the above tensioning objectives may be achieved by having different attachment points for attaching the second chain to the chain-attachment arm on the implement draw-bar. For example if a light tractor is towing a heavy implement the chain should be attached to the chain-attachment arm so that it is further away from the draw-bar, and vice versaxe2x80x94if it is a heavy tractor and light towed implement. In general the attachment points on the chain-attachment arm should be capable of allowing the second chain to have an angle of substantially between 15 degrees to 45 degrees with respect to the draw-bar.
To assist the farmer in repeatedly setting the leaf spring to the correct tension whenever a particular towed implement is connected to the tow-bar of the tractor, the leaf spring may be attached to a load scale indicator device. The load scale indicator device being capable relaying the degree of tension that is being applied to the leaf spring. Consequently, once the farmer has initially experimented towing the implement at different leaf spring tensions; once the correct tension for that implement is found the farmer simply records this for future reference. Thus, the next time this implement is towed the farmer uses the load scale indicator device to set the leaf spring tension to that used previously.
In general, the load scale indicator device may be a spring-balance which is configured so that it is operated via a load being applied to the leaf spring
Of course this should not be seen as limiting as other forms of load scale indicator device are envisaged.
In preferred embodiments the load scale indicator device is also designed to relay to a farmer when the leaf spring or draft control system has reached, or is approaching, an overload condition.
Thus preferred embodiments of the present invention may have a number of advantages over the prior art which may include:
1. It allows the driver of a tractor to select the desired wheel slippage via the draft control system once the apparatus of the present invention has been connected to both the tractor""s three-point linkage and the towed implement.
When the implement is being towed the present invention is then able to convince the hydraulic draft control system of the tractor to believe there is an underground implement in use. Consequently, the draft control system is able to lift or lower the draw-bar of the towed implement so as to transfer load between the implement and the traction axle of the tractor. This load transfer therefore allows the tractor to maintain the desired wheel slippage when external factors such as hills, rocks or muddy ground for example are encountered.
2. It can provide a cost-effective means for overcoming the difficulties currently experienced with towing above ground implements. Thus there is no need to:
a) add ballast to the tractor;
b) increase the size or horsepower of the tractor;
c) have a four wheel drive and/or dual wheel tractor;
as was previously required.
3. Once the apparatus is set up, no further input from the driver of the tractor is required, as the shock absorber and draft control system automatically act to maintain the desired wheel slippage for the tractor.
4. It can transfer load from the towed implements to all the wheels of the tractor (i.e. including the front xe2x80x9csteeringxe2x80x9d wheels).
5. It can increase the productivity of a tractor driver as there is no longer a requirement to add or remove ballast to the tractor. In addition, as no further weight is being added to the tractor (over and above the towed load) fuel consumption is not increased by the present invention.